Magnesium base alloy



Patented June 9, 1942 UNITED STATES MAGNESIUM BASE ALLOY John C. McDonald, Midland, Mich" assignor to The Dow Chemical Company, Midland, Mich, a corporation of Michigan No Drawing. Application December 23, 1940, Serial No. 371,381

2 Claims;

This invention relates to magnesium base alloys and more particularly concerns an alloy of the nature having high tensile and yield strengths associated with a sufiicient degree of formability to render the alloy suitable for forming operations.

Magnesium base alloys are being widely used in the structural arts where a light weight metal is highly desirable, such as for use in making castings, forgings, and the like. However, the use of these alloys in the rolled form"to make sheet metal articles requiring forming operations, such as bending and drawing has not progressed as rapidly due to the fact that, in general, alloys having good formability or ductility permitting relatively sharp bends to be made without the article developing external cracks, usually have inferior: characteristics as regards their tensile and yield strengths.

It is, accordingly, the principal object of the invention to provide a magnesium base alloy satisfactory degree of formability are manifest over the entire range of composition indicated. I have found that, in general, the most satisfactory combination of properties exists when the 5 alloy contains from 5 to 10 per cent of cadmium,

from 0.4 to 0.5 per cent of cerium, from 1 to 5 per cent of zinc, and from 2 to 2.5 per cent of manganese.

The following table, listing some of the prop- 10 erties of rolled sheet metal made from my new quintary alloy and comparing these properties with those of closely related quaternary alloys, illustrates the improvement in tensile and yield strengths of my new alloy over similar proper- 15 ties of the related commercial alloys, and also shows the alloy to have a satisfactorily high degree of formability to permit sheets made therefrom to be subjected to forming operations.

In the table the per cent elongation is .to be go regarded as a measureof the ductility or formability of the alloy.

which can be made into rolled sheet and the like possessing a suflicient degree of ductility or formability at ordinary temperatures to be sharply bent, drawn or otherwise shaped, while having improved tensile and yield strengths.

Other objects and advantages will be apparent as the description of the invention proceeds. My invention resides in the discovery that a magnesium base alloy containing from 1 to 15 per cent of cadmium, from 0.01 to l'per cent, of cerium, 0.3 to 8 per cent of zinc, and 0.01 to 3 per cent of manganese possess the aforementioned desirable properties. The term magnesium used herein and in the appended claims is intended to include magnesium containing impurities ordinarily present. in the commercially pure metal, such as traces of iron, copper, nickel, and silicon. While the properties of improved tensile and yield strengths, associated with a Table Nominal composition in percent (magnesium: remainder) Annealed Cold rolled Yield Tensile Yield Tensile Ce Cd Mn Zn gag? strength strength strength strength me in lbs/sq. in. in lbs./sq. in. in lbs./sq. in. in lbs/sq. in.

The properties set forth above under the term annealed were obtained by first rolling specimens ofalloys at a temperature of 600 F. and thereafter annealing them at various temperatures in a range of from 400 to 500 F. The properties selected for the table were those of the annealed specimens which exhibited the maximum elongation. The properties set forth under the term cold rolled were obtained by subjecting specimens of the alloy which had first been hot rolled at temperatures of 600 F. to additional rolling in the cold state. The properties selected for the table were those of the cold rolled specimens which exhibited the greatest tensile and yield strengths, while having at least a 1 per cent elongation in 2 inches. A comparison of the properties listed in the table shows that the combined strength properties of my new alloy are always superior to out that my new alloy is amenable to solution and precipitation heat treatments, which accordingly modify its properties.

The new alloy may be compounded by any of the methods usually employed for melting an alloying metal with magnesium, such as by add ing the alloying ingredients singly or jointly to a bath of molten magnesium, which is preferably protected from oxidation by a suitable flux, The cerium may be added to the alloy as such, or in the form of Misch-metal. Magnesium-cerium alloys are commonly made up by employing Misch-metal as a source of cerium. It is sometimes desirable to add more than the theoretical amount of Misch-metal since the alloying efliciency is not always 100 per cent and some loss may be incurred.

It is to be understood that the invention is not limited to the specific composition herein disclosed but may take other forms without departing from the scope of the invention.

Iclaim:

1. A magnesium base alloy containing from 1 to 15 per cent of cadmium, from 0.01 to 1 per cent of cerium, from 0.3 to 8 per cent of zinc, from 0.01 to 3 per cent of manganese, and the balance being magnesium.

2. A magnesium base alloy containing from 5 to 10 per cent of cadmium, from 0.4 to 0.5 per cent of cerium, from 1 to 5 per cent of zinc, and from 2 to 2.5 per cen't of manganese.

JOHN c. MCDONALD. 

